Hitherto, an LC filter including a coil and a capacitor has been widely used as a composite electronic component for EMI (Electromagnetic Interference) removal included in an electronic device or the like.
For example, Japanese Unexamined Patent Application Publication No. 2002-009572 discloses such an LC filter.
FIG. 12 shows an existing LC filter 400 disclosed in Japanese Unexamined Patent Application Publication No. 2002-009572.
The LC filter 400 includes a columnar core 101, a winding 102, and electrodes 103 to 106.
The core 101 is formed from alumina or the like and includes a core portion 101a and flange portions 101b and 101c formed at both ends of the core portion 101a. The core portion 101a has a smaller cross-sectional area than the flange portions 101b and 101c. 
The winding 102 is composed of a metallic copper wire whose surface is coated with an insulation, and is wound on the core portion 101a. 
The electrodes 103 and 105 are formed on the surface of the one flange portion 101b of the core 101. The electrode 103 and the electrode 105 are separated from each other by a gap. One end portion of the winding 102 is connected to the electrode 103. When the LC filter 400 is used, the electrode 105 is connected to a ground electrode of a circuit board or the like.
Similarly, the electrodes 104 and 106 are formed on the surface of the other flange portion 101c of the core 101. The electrode 104 and the electrode 106 are separated from each other by a gap. The other end portion of the winding 102 is connected to the electrode 104. When the LC filter 400 is used, the electrode 106 is connected to the ground electrode of the circuit board or the like.
That is, in the LC filter 400, the core portion 101a and the winding 102 form a coil portion, the electrode 103 and the electrode 105, which are separated from each other by the gap, form one capacitor portion with the flange portion 101b as a dielectric, and the electrode 104 and the electrode 106, which are separated from each other by the gap, form another capacitor portion with the flange portion 101c as a dielectric. The LC filter 400 is configured as a π type LC filter by the coil portion and the capacitor portions.